Enable building allConfigurations for corefx in source-build

[weshaggard]

We need to build all packages not just .NET Core app packages when we are in offline source-build mode. However the allconfigurations leg has never worked correctly on non-windows so we need to iterate on it in order to enable.

We need to essentially undo 617ebe0.

[weshaggard]

When we enable this we need to take into account #184

[weshaggard]

@bartonjs this is likely something we will need to do at some point to fully build the packages people depend on upstack.

[dagood]

Status:

I worked on this for a while. I'm able to make CoreFX build AllConfigurations on linux after a few changes. WIP branch: master...dagood:corefx-all

Initially I tried to use a single command to build -allconfigurations and the vertical for the current platform within the same build context. That has complications (dotnet/corefx#34332 (review)) so I abandoned it and instead first execute a build command for -allconfigurations, then another build command for the vertical.

The build passes with AllConfigurations included, but it brings in a ton of new prebuilts: 68c0578. Main categories are:

1. Old versions of CoreFX packages to harvest from.
2. CoreCLR builds for other platforms (e.g. to compile against to build Windows assemblies on Linux).
3. A CoreCLR build for the current platform. When I tried to use the source-built CoreCLR, it failed:
   • The locally built version doesn't necessarily line up with a Microsoft-built version for the other platforms.
   • Building AllConfigurations might make the coupling between CoreCLR and CoreFX more brittle than before with only one vertical. I don't know for sure if this caused the errors I was seeing, though. This might have been an issue with portable builds.
   • We could look into adding something like AllConfigurations to CoreCLR as well. ("AllPlatforms", "AllRuntimes"?) If CoreFX only needs CoreCLR's managed outputs, it might be feasible.
4. A little extra build tooling. (I haven't investigated to see if we can source-build it.)

I experimented with forcing them to be treated as reference packages, but hit problems with resource files in the ILDasm/ILAsm round trip.

[dseefeld]

Fixed with #1173